Sequential electromagnetic control circuit for well explosive devices



. Spt. 28, 1965 L.-FOSTER 3,209,210 OMAGNETIC CONTROL CIRCUIT EXPLOSIVE DEVICES J. SEQUENTIAL ELECTR 2 Slhe'ets-Sh'eet 1 I I FOR.WELL Original Filed Aug. 15, 1945 r. e w m w W INVENTOR.

Sept. 28, 1965 J. L. FOSTER 3,209,210

SEQUENTIAL ELECTROMAGNETIC CONTROL CIRCUIT WELL EXPLOSIVE DEVICES FOR Qriginal Filed Aug. 15, 1946 2 Sheets-Shet 2- Fi.6 J2

7o- 6! s4i\:

Fi 6- 7 76 77 f 70 Q James L ewis Foster 1 INVENTOR.

Hi6 Agent 1 claim. (or. 317-139 This application is a divisional application of my prior application Ser. No. 357,589, filed May 26, 1953, now Patent No. 2,919,646, granted January 5, 1960, which application is a continuation of my prior application Ser. No. 690,762, filed August 15, 1946, for Well Explosive Devices; which application in turn was a continuation-inpart of my prior application for Well Explosive Devices, filed Dec. 2, 1942, Ser. No. 467,657, now Patent No. 2,408,419, granted Oct. 1, 1946; which in turn was a division of my prior application on Process for Treating Wells, filed March 17, 1939, Ser. No. 262,531, now Patent No. 2,307,729, granted Jan. 5, 1943.

This invention relates to improvements in well explosive devices adapted for the discharge of an explosive projectile in a subterranean formation to loosen up the formation and to facilitate the flow of oil or other fluid from an oil bearing formation into the bore hole of a well for withdrawal therefrom.

Heretofore, it has been common practice to lower large charges of high explosives into a well and to detonate these charges by mechanical or time-clock means. These charges, which consist of from ten quarts to five hundred quarts of pure nitroglycerin, are dangerous to the workmen handling them, dangerous to public safety, since they must be transported over the public highways, and when detonated, frequently do extensive damage to the well casing and well equipment. The reason these charges must be so large, is that they depend entirely on concussion and reverberation to achieve the desired result of loosening and removing that part of the formation immediately adjacent the bore hole, wherein they are approximately axially disposed at the time of detonation.

By placing a small amount of the explosive at various points in the earth formation and by detonating this explosive, more advantageous results may be obtained than by placing a large amount of explosive within the bore hole of the well and detonating it therein.

While the drawings show one form of the apparatus for practicing the invention, it is to be understood that the invention relates to the provision of more advantageous placing of explosives contained in projectiles at a point in the earths stratum removed from the bore hole, and to projectiles for this purpose, so that the portion of the stratum lying between the point of explosion and the bore hole will be driven toward the bore hole by the force of the explosion.

It is obvious that varied results, such as blasting down a portion of the wall of the well, driving gathering holes with basins at the outer ends thereof, providing entries for formation solvents, providing enlarged sections in the bore hole for the anchoring of cement bridges, and other functions, may be produced by varying the force of the explosives involved in the invention, and by varying the types of projectiles used. These variations are to be Fri was considered within the scope of the invention herein disclosed.

The accompanying drawings show a preferred embodiment of the invention, together with a modification thereof, in which like reference characters designate like parts in the several views thereof, in which:

FIG. 1 is a fragmentary, vertical section of an earth formation, showing the tool partly in elevation and partly in section, disposed in a well;

FIG- 2 is a fragmentary, horizontal section through the tool, taken on the line 2-2 of FIG. 1, looking in the direction indicated by the arrows;

FIG. 3 is a longitudinal sectional view through a form of projectile used in connection with the tool;

FIG. 4 is a view similar to FIG. 3, but of a modified form of projectile to be used in the tool;

FIG. 5 is a diagrammatic view of a wiring diagram for sequentially firing a plurality of explosive charges within the tool;

FIG. 6 is a longitudinal sectional view of a further modified form of projectile;

FIG. 7 is a longitudinal sectional view of a still further modified form of projectile; and

FIG. 8 is a longitudinal sectional view through the detonator for the projectiles as shown in FIGS. 6 and 7.

With more detailed reference to the drawing, the numeral 1 designates the body of a tool which carries a plurality of radially disposed explosive chambers or cannons 2 which are preferably spaced along the length of the tool, and preferably being turned in different radial directions thereto. These cannons have removable barrels 3 which may be taken out of the tool 1, since they are removably placed in sockets 4 which are formed in the tool 1. The removable barrels 3 are held in place within the respective recesses 7 by means of bolts 6. Within the outer end of the barrel 3 is disposed the threaded bushing 8 which engages a shear ring 11 and causes the ring to seat upon gasket 5, which prevents moisture from entering the powder chamber 9. The threaded bushing 8 forms an extension of the cannon barrel and is removed each time a new projectile is inserted.

Before the tool 1 is inserted into a well, an explosive charge is placed within powder chamber 9 in each of the cannon bores or chambers 2 behind an explosive projectile 10 or 10 therein, upon which projectile an expansive shear ring 11 has been fitted, which is slipped into an annular recess 12 in cannon bore 2.

A percussion cap 13 is fitted into an opening 14 in the cannon barrel 3, longitudinally of the tool, so that a firing pin 15 will detonate the cap 13 and the adjacent explosive charge in chamber 9, upon the striking of the firing pin 15 by a hammer 16. The hammer 16 com prises an axial shaft, which shaft has one end thereof conical and the other end thereof being blunt, and a disc-like, cylindrical member secured to the axial shaft to form a magnetically attractable member which is spaced from and is operated by an electro-magnetic coil or solenoid 17 when electrical energy is supplied thereto. The entire solenoid mechanism is contained in a casing 18 and may be inserted into or removed from the tool through the recess 4 therein. The casing 18 of the solenoid mechanism has inwardly extending abutments at the lower end thereof and has an axially apertured cover at the opposite end, which cover is exteriorly threaded to threadably engage the interiorly threaded portion of the casing 18. The casing 18 is exteriorly screw threaded for a portion of the length of the upper end thereof to threadably engage threads within a longitudinal recess which is formed within the body of the tool 1. The coil spring 26 has one end thereof in bearing engagement with the cylindrical, disc-like portion of hammer 16 and the other end of the coil spring is in bearing engagement with the axially apertured cover of the casing 18 to hold the cylindrical, disc-like portion of the hammer 16 in seated relation against the abutments atthe lower end of the casing 18. With the hammer 16 thus positioned and being a spaced distance from solenoid coil 17, movement of the cylindrical, disc-like portion of the hammer 16 toward the solenoid -coil 17 is made possible, when the coil is electrically energized, so that the blunt end of the axial shaft 16 will strike the firing pin 15 to detonate an explosive charge in chamber 9, as is brought out above.

A single wire, with grounded return circuit, is shown in FIG. and a relay switch is connected within this wired circuit 21 and has connection with the solenoid which is next to be operated, so that the projectile may be subsequently fired from cannon bores 2, by closing and opening a switch 19 in said circuit (FIG. 5), which switch is located at the ground surface, or at the mouth of the well. Upon closing the switch 19, a source of electrical energy, such as battery 20, is connected with the circuit 21 leading to the solenoids 17, which are in parallel with the circuit through secondary switches.

A switch arm 22 rests on a contact plate 23 (FIG. 2) which closes the circuit to the coil 17 and actuates the hammer 16 by the force exerted in magnetic coil 17. As the hammer 16 is moved to strike firing pin 15 (FIG. 1),

a conical, pointed end 24 of the axial shaft of the hammer, which pointed end 24 is made of fibre or other insulating material and which normally holds arm 22 retracted, is withdrawn and permits the switch arm 22 to be moved into the position shown in dotted lines and indicated at 22' (FIG. 2), by a spring 45 acting on the arm 22 until said switch arm is stopped by a stop pin 46.

In the position just described, the contact point 25 is still in contact with the plate 23, although having moved to the opposite side of the axis of the hammer 16. However on the breaking of the circuit by the manual release of the switch 19, the solenoid 17 is de-energized, thereby releasing the hammer 16, and upon return of the hammer 16, under the pressure of a coil spring 26 hearing thereagainst, the pointed end 24 will push the switch point 01f the contact plate 23 against a contact 23, to the dotted line position, as indicated at 22 (FIG. 2). By this movement of the switch arm 22, the first solenoid is entirely disconnected from the circuit and remains deenergized until the tool is removed from the well and the mechanism reset when a new charge is inserted. A plugged opening 27 is provided through the wall of the tool 1 for the insertion of an instrument against the switch arm 22 for resetting same, as shown in FIG. 2.

When the switch arm 22 moves to the dotted line position 22" and engages contact 23', after firing the first charge, this closes the circuit 21 to the next succeeding solenoid 17 which is then ready to be fired by again closing the switch 19, as described. This operation is repeated until all of the charges have been fired.

The wire 21 is shown schematically in FIG. 1, for the sake of clearness; however, it is to be understood that the tool is to be drilled both longitudinally and transversely to accommodate the wire to the respective solenoids,

designated a, b, and c in FIG. 5. The wire is shown leading onward from solenoid c, as any number of discharge units may be used. When the tool is cross-drilled, the holes will be plugged in the usual manner.

Several types of penetration are desirable, particularly for oil wells, four of which are shown. One type is indicated at A, where an explosive projectile is shot into the stratum for a short distance and the force of the explosive is used to blow the formation toward the well. In this manner, a formation, which has become sealed with paratfin, mud or other foreign material which renders the formation non-productive of oil, may be removed by placing the projectile a short distance beyond the wall of the bore hole and detonating it, so that the foreign substances will be loosened, and may be cleaned from the well. A new porous surface is thus produced which has a larger exposed area, thereby giving the well greater productivity.

Another form of shot which may be placed, is that indicated by dotted outline at B. The amount of explosive placed in chamber 2 is increased, so as to drive the projectile a greater distance into the stratum, than the projectile shown at A. This projectile may be so constructed that it will be blown into bits, as shown in FIG. 4, each of the fragments cutting a channel in the stratum, and in this manner a passage is formed for some distance out into the stratum with a basin at the outer end, and passages radiating from said basin, thus opening up producing stratum, or permitting chemicals to be introduced into certain types of formation, where they Will Work with greater rapidity and effectiveness, than if introduced into the immediate bore hole of the well.

Two types of projecticles are shown in FIGS. 3 and 4, respectively. The type shown in FIG. 3 has a round nose 28, which is fitted with a firing pin 29 which strikes percussion cap 30. This ignites a fuse 31, which may be varied in length, to delay the firing of the explosive charge 32 until the projectile has traveled the desired distance into the stratum. The interior of the projectile is accessible for loading, as by forming it in sections which are screw-threaded together at 33. The nose 28 is crushed upon striking a formation of sufficient hardness, and this drives the pin 29 against percussion cap 30. A short fuse is shown to indicate the placing of the explosive charge only a short distance from the bore hole. The shear ring 11 retains the projectile within the cannon barrel until the greater part of the explosive charge is burned. In this manner the full effectiveness of the charge is obtained, upon the shearof the expansive shear ring 11.

The form of projectile, as shown in FIG. 4, is preferably made of cast metal in two parts which are screwthreaded together, as shown at 33, and which has annular and longitudinal grooves 34 and 35, respectively, disposed within the chamber 36 which is designed to carry the explosive charge. This form is shown to have a sharp nose and a pointed firing pin 38, which may be advantageous in penetrating hard types of formation.

The pointed firing pin 33 is in position to strike a per ncussion cap 39 upon impact with a substantially nonyielding formation. To prevent the firing pin 38 from striking the percussion cap 39 too readily, a shear pin 40 is provided which is in engagement with the firing pin and which will shear when the projectile is driven into hard formation. Upon the detonation of cap 39 a powder train 41 will be ignited. The length of the powder train, together with the speed with which the powder burns will be computed so as to permit the projectile to travel the desired distance intov the formation before detonating the explosive contained in the chamber 36. This type of projectile will form a long passage, with a basin at the end thereof, and with passages radiating outward therefrom, in the formation as indicated at B in FIG. 1.

Other forms of projectiles are shown in FIGS. 6 and 7, each of which is adapted to be filled with a high explosive powder and provided with a detonator to ignite and discharge the powder when the projectile has penetrated the formation to the desired extent.

In the form of the invention shown in FIG. 6, the proectile is designated generally at 50, which projectile is in the form of shell having a pointed forward end 51 of conical shape to penetrate the formation. The shell 50 has a surrounding rib 52 at the rear end thereof which is adapted to be secured in the same manner of the ring 11, described above, for holding the projectile in the tool. The interior of the projectile body50 is filled with a high explosive powder 53 confined therein by a plug 54, which is screwed into the back end of the body and forms a seal for the explosive powder.

The form of projectile shown in FIG. 7 is similar to that illustrated in FIG. 6, and likewise has body 60 provided, nevertheless, with a curved tapered nose portion 61. The high explosive charge 63 is packed in a chamber of somewhat larger capacity to accommodate a greater quantity of explosive than is provided in FIG. 6, and is confined by a plug 64, which seals the open side of the explosive chamber.

In each of the forms, as shown in FIGS. 6 and 7, a detonator 70 is contained and sealed within the explosive charge, the construction of which is shown more in detail in FIG. 8. Other suitable forms of detonators may be used, if desired, although that illustrated has advantages in the construction and use thereof.

As shown in FIG. 8, the detonator 70 is formed with a cylindrical tube 71, one end of which is open initially and adapted to be closed by a seal 72. The opposite end is adapted to be packed with a primer charge of explosive, as indicated at 73, which charge has suflicient explosive power to detonate the explosive charge 53 or 63 in the projectile.

The primer charge 73 is confined in the tube 71 by an explosive pellet which is slow burning and is known as a delay pellet as indicated at 74. Adjacent the delay pellet, but spaced therefrom, is an explosive element 75, preferably formed of an explosive compound, such as the phosphorus compound used commercially in forming match heads and which is adapted to be ignited by friction in the customary manner of striking a match on an abrasive surface. The explosive element 75 has an orifice therethrough, through which passes a thread 76, one end of which is coiled in the space between the element 75 and the delay pellet 74, while the opposite end of said thread 76 is attached to a weight such as ball 77. The thread 76 is flexible, but is coated with a suitable abrasive material to cause an ignition of the explosive element 75, as the thread is drawn through the orifice therein.

The ball 77 normally is confined in the retracted position shown in FIG. 8, by an element 78, which may be of tissure paper or a frangible disc which may be broken by force imparted to the ball, although normall this restraining element 78 will confine the ball in position. This element 78 is spaced from the end of the tube 71 so that the force imparted to the ball by a projecting movement of the projectile and its arrest in the formation will cause a continued movement of the ball after breaking the arresting element 78 and it will continue to travel through the length of the space in tube 71.

This action of the ball will draw out the abrasive coated thread through the explosive element 76 and thereby cause friction on said element to ignite the phosphorus compound. This, in turn, will ignite the delay pellet 74, but because of its slow burning character, it will not immediately ignite the primer charge 73 until the projectile has traveled a required depth into the earth formation, as described above. When the delay pellet burns through to the primer charge 73, the latter is ignited, thereby causing an explosion of the detonator, which in turn, ignites and detonates the explosive charge in the projectile. This will cause an explosion in the formation at the desired point according to the character of the projectile used, and the delay action thereof, which however, will loosen up the formation and cause the oil or other fluid to flow into the well in the manner described above.

The tool may be lowered into the well by any suitable means, such as a pipe 42, or a cable. If used on a drill 6 stem, it can be screwed together in such manner that the direction of the cannon barrels can be determined, as by matching index marks43 (FIG. 1) as the joints are screwed together. In this manner, the direction in which the projectile is fired may be determined from the surface.

The tool may be used to obtain samples of formation in proximity of the detonated projectile, as the force of the explosion of the projectile 10 or 10' will force a portion of the formation into a cannon barrel, as indicated at 44, which portion may be removed from the well for analysis.

On reloading the device, a new gasket 5 and a new shear ring 11, as well as a new projectile, will be required, as the projectile will shear these each time the cannon is detonated.

The lower end of the tool is preferably tapered to a point to facilitate its insertion into, as well as its removal from the well, after the explosion of the projectiles, when the explosives would have forced a quantity of the formation into the bore hole.

Having thus described the invention, what is claimed is:

A well explosive device having a plurality of cannon barrels, each of which has a firing pin, comprising in combination;

(a) a plurality of cylindrical casings,

(1) an inwardly extending abutment formed in each said cylindrical casing,

(b) a cylindrical hammer, including a disc-like member and an axial shaft, fitted in guided relation within each said cylindrical casing,

( 1) each said axial shaft having a conical point on one end thereof,

(2) the other end of each axial shaft being relatively blunt,

(c) a hollow solenoid coil fitted within each said cylindrical casing a spaced distance from said inwardly extending abutment,

(d) a coil spring positioned within each hollow solenoid coil and surrounding each said axial shaft, said spring having one end thereof in engagement with a face of said disc-like member of said hammer, the other end of said spring being in engagement with the inner face of said axially apertured cover of each said casing,

(e) said axial shaft of each hammer having the blunt end thereof adjacent a firing pin and being in axial alignment therewith of each cannon barrel of said well explosive device,

(f) a switch positioned within said well explosive device adjacent the conical, pointed end of each said axial shaft, and having a first contact and a second contact,

(1) said switch having a spring actuated switch arm with a further contact thereon, which normally is held in contact relation with said first contact when in a first position,

(2) said conical point of each axial shaft being positioned to permit said switch arm to shift from one side of the axis of said axial shaft to a second position on the opposite side of the point of each said axial shaft upon energization of said solenoid coil,

(3) said switch arm being movable out of contact with said first contact by spring pressure of said coil spring upon de-energization of said solenoid coil to urge said switch arm into contact relation with said second contact upon reengagement of said conical point of each said shaft with said switch arm,

(g) an electrical circuit,

(1) a manually operated initiating switch in said electrical circuit to energize and de-energize a first solenoid coil,

(2) said manually operated initiating switch being selectively operable to actuate said switch arms successively to energize and de-energize' successive solenoid coils independently and to automatically open said circuit leading to each de-energized solenoid coil to enable subsequent solenoid coils to be energized and de-energized and switch arms actuated thereby to open each circuit to a solenoid coil so de-energized.

References Cited by the Examiner UNITED STATES PATENTS Re. 16,851 1/28 James 20094 8 Es'chholz 3l5246 Butler 200-87 Richardson 317-140 Sippel .20087 Yarbrough 891.02 Mohaupt l0256 Catlin l0256 SAMUEL BERNSTEIN, Primary Examiner.,

10 ARTHUR M. HORTON, Examiner. 

